1. Field of the Invention
The invention relates in general to a semiconductor structure and a manufacturing method thereof, and more particularly to a semiconductor structure related to a bipolar junction transistor (BJT) and a manufacturing method thereof.
2. Description of the Related Art
A bipolar junction transistor (BJT) is one of the most important semiconductor devices in modern times. The BJT is a three-terminal device that comprises two inseparable PN junctions. The terminals are called emitter, base, and collector. The BJT device conducts current with electrons and holes simultaneously and has the advantages of high speed and large current allowance in a small device, making the BiCMOS structure comprised of the BJT and CMOS devices popularly used to enhance operational speed of the transistor.
In design of the bipolar junction transistor, the dopant concentration of the emitter is increase to enhance the injection efficiency of the emitter. However, the breakdown voltage between the emitter and base is relatively decreased, thus causing the performance of the bipolar junction transistor worse.